Process for Preparing Articles Having Anti-Fog Layer by Layer Coating and Coated Articles Having Enhanced Anti-Fog and Durability Properties

ABSTRACT

Disclosed are processes for preparing articles having anti-fog properties, comprising providing a substrate having at least one main surface coated with an intermediate coating obtained by applying and at least partially curing an intermediate coating composition comprising at least one monoepoxysilane and/or an hydrolyzate thereof and at least one polyepoxy monomer comprising at least two epoxy groups, forming onto said intermediate coating at least one bi-layer, and curing said at least one bi-layer by heating at a temperature of 150° C. or less at atmospheric pressure and in the absence of added water steam. Also disclosed are articles made and/or makeable by these processes.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a process for preparing an article bearing animproved anti-fog layer-by-layer coating and to the articles bearing ananti-fog layer-by layer coating obtained by said process, moreparticularly optical and ophthalmic articles, especially ophthalmiclenses for eyeglasses.

The invention is based on the use of a specific intermediate coatingenhancing anti-fog properties and adhesion of said anti-foglayer-by-layer coating, along with a specific heating step of thelayer-by-layer coating.

2. Description of Related Art

It is known in the art that a layer-by-layer (LbL) coating can beassembled on a substrate from species having opposite charges. Moreprecisely, positively and negatively charged polyelectrolytes can bealternately deposited on a substrate.

For this purpose, at least two different polyelectrolyte solutionshaving opposite charges, or a polyelectrolyte solution and ananoparticle solution having opposite charges, may be used to form theLbL coating.

As known in the art, a polyelectrolyte is a polymer having a substantialportion of its repeating units bearing an electrolyte group. Thesegroups are ionic or ionizable groups, especially in aqueous solutions.

Other known LbL coatings include a plurality of bilayers alternatelycomprising oppositely charged nanoparticles.

By selecting the materials of the layers and the deposition processconditions, such films can be anti-reflective, hydrophilic orsuperhydrophilic, hydrophobic or superhydrophobic.

LbL coatings having hydrophilic properties may also have anti-fogproperties.

US 2007/0104922 describes superhydrophilic LbL coatings that can beantireflective and anti-fog. i.a. poly(allylamine hydrochloride)/SiO₂LbL coatings.

A disadvantage of the anti-fog LbL coatings is that such coatingsexhibit generally poor mechanical properties, especially poor adhesionto organic substrates, either naked or coated by classical hard coats.Mechanical properties of LbL coatings have been increased by calcinationtreatment, generally at high temperature (typically 550° C.).

A disadvantage associated to this technique is that it cannot be appliedon any organic substrates and is only adapted to substrates that canwithstand high temperature like glass substrates.

In the article “Hydrothermal Treatment of Nanoparticle Thin Films forEnhanced Mechanical Durability” Z. Gemici et al., Langmuir 2008, 24,2168-2177, a hydrothermal treatment implemented at around 125° C., ofdifferent LbL coatings is described in order to improve mechanicaldurability of these coatings and avoid delamination, especially on apolycarbonate (PC) substrate.

A typical example of a LbL coating is either a polymer-nanoparticlecoating made alternatively from a positively chargedpoly(diallyidimethyl ammonium chloride) and negatively charged silicananoparticles, or an all-nanoparticle coating assembled alternativelyfrom positively charged 3-aminopropyl silane modified silica (ortitania) nanoparticles and negatively charged silica nanoparticles.After a hydrothermal treatment, such LbL coating has improved abrasionresistance.

US 2008/0038458 describes a hydrothermal calcination of TiO₂/SiO₂ LbLcoatings, typically at a pressure in the range of 10 psi to 30 psi attemperature less than 500° C.

One disadvantage of the technique, along with the necessity of using anautoclave, is that the hydrothermal treatment affects the anti-fogproperties of the coating, as explained in US 2008/038458 paragraph[0046]: the coating can lose its anti-fog properties.

Consequently, it is desirable to provide a new and simple process ofpreparation of anti-fog LbL coatings having good or improved anti-fogproperties, along with good mechanical properties such as improvedadhesion to the substrate and/or improved abrasion resistance.

U.S. Pat. No. 6,984,262 describes a coating composition adapted toenhance the adhesion of a polymeric coating or film applied to asubstrate.

This adhesive coating comprises at least one specific silane couplingagent, at least partial hydrolyzates thereof in a concentration greaterthan 25% and an adhesion enhancing amount of an epoxy-containingmaterial comprising at least two epoxy groups.

There is no disclosure of an anti-fog LbL coating as the polymericcoating and no disclosure that the adhesive coating can improve theanti-fog properties of a LbL system.

SUMMARY OF THE INVENTION

An object of the invention is to improve the anti-fog properties ofanti-fog LbL coatings.

Another object of the invention is to improve the mechanical durabilityof anti-fog LbL coatings, especially adhesion properties, for a widerange of substrates, especially organic substrates while keeping thedeposition process of such anti-fog LbL coating as simple as possible.

A further object of the invention is to provide an anti-fog LbL coatinghaving the improved anti-fog and mechanical properties mentioned abovewithout concurrently decreasing its optical transparency in the visiblerange.

The present inventors have found that the anti-fog properties along withthe durability of a LbL coating are improved by using a specific processfor preparing an article having anti-fog properties, comprising:

-   -   a) providing a substrate having at least one main surface coated        with an intermediate coating obtained by applying and at least        partially curing an intermediate coating composition comprising        at least one monoepoxysilane and/or a hydrolyzate thereof and at        least one polyepoxy monomer comprising at least two epoxy        groups,    -   b) forming onto said intermediate coating at least one bi-layer        obtained by:    -   b1—forming a first layer by applying a first layer composition        on said intermediate coating, said first layer composition        comprising at least one compound A having a first electric        charge,    -   b2—forming a second layer by applying a second layer composition        directly on said first layer, said second layer composition        comprising at least one compound B having a second electric        charge which is opposite to said first electric charge,        compounds A and B being independently chosen from        polyelectrolytes, SiO₂ nanoparticles comprising ionic groups and        TiO₂ nanoparticles comprising ionic groups, with the proviso        that at least one of said first and said second layer comprises        SiO₂ nanoparticles comprising ionic groups and/or TiO₂        nanoparticles comprising ionic groups, preferably SiO₂        nanoparticles comprising ionic groups,    -   c) curing said at least one b-layer by heating at a temperature        of 150° C. or less, preferably 140° C. or less, more preferably        130° C. or less, even better 120° C. or less, at atmospheric        pressure and in the absence of added water steam.

Preferably, one of the layers of said at least one bi-layer comprisesSiO₂ nanoparticles comprising ionic groups and the other layer of saidat least one bi-layer comprises at least one oppositely chargedpolyelectrolyte.

In another preferred embodiment, the intermediate coating is coated witha plurality of bi-layers stacked onto each other, with the proviso thatthe second electrostatic charge of the at least one compound B comprisedin the second layer of each bi-layer is opposite to the firstelectrostatic charge of the at least one compound A comprised in thefirst layer of the subsequent bi-layer.

When the intermediate coating is coated with a plurality of bi-layersstacked onto each other, compounds A (or B) in one bi-layer andcompounds A (or B) in another bi-layer can be the same or different.

The invention also relates to an optical article comprising a substratehaving an anti-fog LbL coating obtainable by implementing the abovedescribed process.

In one embodiment of the invention, the monoepoxysilane has preferablyformula:

R_(n′)YSi(X)_(3-n′)  (1)

in which the R groups are identical or different and representmonovalent organic groups linked to the silicon atom through a carbonatom, Y is a monovalent organic group linked to the silicon atom througha carbon atom and containing one epoxy function, the X groups areidentical or different and represent hydrolyzable groups or hydrogenatoms, and n′ is 0 or 1.

The intermediate coating of the invention improves the adhesion betweena substrate and the anti-fog LbL coating, but also improves or maintainsthe anti-fog performance of the outermost bi-layer coating, when thesubstrate is coated with several bi-layers according to the invention.

The intermediate coating can also be applied on hard coated lenses suchas PC Airwear® lens substrates.

Other objects, features and advantages of the present invention willbecome apparent from the following detailed description. It should beunderstood, however, that the detailed description and the specificexamples, while indicating specific embodiments of the invention, aregiven by way of illustration only, since various changes andmodifications within the spirit and scope of the invention will becomeapparent to those skilled in the art from this detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other objects, features and advantages of the presentinvention will become readily apparent to those skilled in the art froma reading of the detailed description hereafter when considered inconjunction with the accompanying drawings, wherein FIG. 1 exhibits thedifferent deposition steps of the LbL coating and FIG. 2 exhibits thestructure of the resulting LbL coating.

DETAILED DESCRIPTION OF THE INVENTION AND PREFERRED EMBODIMENTS

The terms “comprise” (and any grammatical variation thereof, such as“comprises” and “comprising”), “have” (and any grammatical variationthereof, such as “has” and “having”), “contain” (and any grammaticalvariation thereof, such as “contains” and “containing”), and “include”(and any grammatical variation thereof, such as “includes” and“including”) are open-ended linking verbs. They are used to specify thepresence of stated features, integers, steps or components or groupsthereof, but do not preclude the presence or addition of one or moreother features, integers, steps or components or groups thereof. As aresult, a method, or a step in a method, that “comprises,” “has,”“contains,” or “includes” one or more steps or elements possesses thoseone or more steps or elements, but is not limited to possessing onlythose one or more steps or elements.

Unless otherwise indicated, all numbers or expressions referring toquantities of ingredients, ranges, reaction conditions, etc. used hereinare to be understood as modified in all instances by the term “about.”

When an optical article comprises one or more surface coatings, thephrase “to deposit a coating or layer onto the optical article” meansthat a coating or layer is deposited onto the outermost coating of theoptical article, i.e. the coating which is the closest to the air.

A coating that is “on” a side of a lens is defined as a coating that (a)is positioned over that side, (b) need not be in contact with that side,i.e., one or more intervening coatings may be disposed between that sideand the coating in question, and (c) need not cover that sidecompletely.

The optical article prepared according to the present invention is atransparent optical article, preferably a lens or lens blank, and morepreferably an ophthalmic lens or lens blank. The optical article may becoated on its convex main side (front side), concave main side (backside), or both sides using the process of the invention.

Herein, the term “lens” means an organic or inorganic glass lens,comprising a lens substrate which may be coated with one or morecoatings of various natures.

The lens substrate may be made of mineral glass or organic glass,preferably organic glass. The organic glasses can be eitherthermoplastic materials such as polycarbonates and thermoplasticpolyurethanes or thermosetting (cross-linked) materials such asdiethylene glycol bis(allylcarbonate) polymers and copolymers (inparticular CR-39® from PPG Industries), thermosetting polyurethanes,polythiourethanes, polyepoxides, polyepisulfides, poly(meth)acrylatesand copolymers based substrates, such as substrates comprising(meth)acrylic polymers and copolymers derived from bisphenol-A,polythio(meth)acrylates, as well as copolymers thereof and blendsthereof. Preferred materials for the lens substrate are polycarbonates(PC) and diethylene glycol bis(allylcarbonate) polymers, in particularsubstrates made of polycarbonate.

The surface of the article onto which the intermediate coating will beapplied may optionally be subjected to a pre-treatment step intended toimprove adhesion, for example a high-frequency discharge plasmatreatment, a glow discharge plasma treatment, a corona treatment, anelectron beam treatment, an ion beam treatment, an acid or basetreatment.

The intermediate coating used in the process of the invention may bedeposited onto a naked substrate or onto the outermost coating layer ofthe substrate if the substrate is coated with at least one surfacecoating. Said at least one surface coating may be, without limitation,an impact-resistant coating (impact resistant primer), an abrasionand/or scratch resistant coating, a polarized coating, a photochromiccoating or a dyed coating.

The impact-resistant coating which may be used in the present inventioncan be any coating typically used for improving impact resistance of afinished optical article. This coating generally enhances adhesion ofthe abrasion and/or scratch-resistant coating on the substrate of thefinished optical article. By definition, an impact-resistant primercoating is a coating which improves the impact resistance of thefinished optical article as compared with the same optical article butwithout the impact-resistant primer coating.

Typical impact-resistance primer coatings are (meth)acrylic basedcoatings and polyurethane based coatings, in particular coatings madefrom a latex composition such as a poly(meth)acrylic latex, apolyurethane latex or a polyester latex.

Polyurethane-polyester latexes are commercially available from ZENECARESINS under the trade name Neorez® (e.g., Neorez® R-962, Neorez® R-972,Neorez® R-986, Neorez® R-9603) or BAXENDEN CHEMICALS, a subsidiary ofWITCO Corporation, under the trade name Witcobond® (e.g., Witcobond®232, Witcobond® 234, Witcobond® 240, Witcobond® 242).

The abrasion- and/or scratch-resistant coating which may be used in thepresent invention can be any coating typically used for improvingabrasion- and/or scratch-resistance of a finished optical article ascompared to a same optical article but without the abrasion- and/orscratch-resistant coating.

Preferred abrasion- and/or scratch-resistant coatings are (meth)acrylatebased coatings and silicon-containing coatings. The latter are morepreferred and are disclosed, for example, in French patent applicationFR 2702486, which is incorporated herein by reference.

The intermediate coating is prepared from an intermediate coatingcomposition, which may be a solution or dispersion, both terms beingmerged in the present patent application. These terms refer to a mixtureof components which generally is uniform at the macroscopic scale(visually) and are not related to a particular solubility state orparticle size of said components.

Said curable intermediate composition comprises at least onemonoepoxysilane and/or its hydrolyzate and at least one polyepoxymonomer.

Preferred monoepoxysilanes are di or tri alkoxysilanes bearing one epoxygroup.

The monoepoxysilane is preferably a compound of formula:

R_(n′)YSi(X)_(3-n′)  (I)

in which the R groups are identical or different and representmonovalent organic groups linked to the silicon atom through a carbonatom, Y is a monovalent organic group linked to the silicon atom througha carbon atom and containing one epoxy function, the X groups areidentical or different and represent hydrolyzable groups or hydrogenatoms, and n′ is 0 or 1.

The X groups may independently and without limitation represent H,alkoxy groups —O—R¹, wherein R¹ preferably represents a linear orbranched alkyl or alkoxyalkyl group, preferably a C₁-C₄ alkyl group,acyloxy groups —Q—C(O)R³, wherein R³ preferably represents an alkylgroup, preferably a C₁-C₆ alkyl group, and more preferably a methyl orethyl group, halogen groups such as Cl and Br, amino groups optionallysubstituted with one or two functional groups such as an alkyl or silanegroup, for example the NHSiMe₃ group, alkylenoxy groups such as theisopropenoxy group, trialkylsiloxy groups, for example thetrimethylsiloxy group.

The X groups are preferably alkoxy groups, in particular methoxy,ethoxy, propoxy or butoxy, more preferably methoxy or ethoxy. In thiscase, compounds of formula I are alkoxysilanes.

The integer n′ defines two groups of compounds I: compounds of formulaRYSi(X)₂ and compounds of formula YSi(X)₃. Among these compounds,epoxysilanes having the formula YSi(X)₃ are preferred.

The monovalent R groups linked to the silicon atom through a Si—C bondare organic groups. These groups may be, without limitation, hydrocarbongroups, either saturated or unsaturated, preferably C₁-C₁₀ groups andbetter C₁-C₄ groups, for example an alkyl group, preferably a C₁-C₄alkyl group such as methyl or ethyl, an aminoalkyl group, an alkenylgroup, such as a vinyl group, a C₆-C₁₀ aryl group, for example anoptionally substituted phenyl group, in particular a phenyl groupsubstituted with one or more C₁-C₄ alkyl groups, a benzyl group, a(meth)acryloxyalkyl group, or a fluorinated or perfluorinated groupcorresponding to the above cited hydrocarbon groups, for example afluoroalkyl or perfluoroalkyl group, or a (poly)fluoro or perfluoroalkoxy[(poly)alkyloxy]alkyl group.

The most preferred R groups are alkyl groups, in particular C₁-C₄ alkylgroups, and ideally methyl groups.

The monovalent Y group linked to the silicon atom through a Si—C bond isan organic group since it contains one epoxy function. By epoxyfunction, it is meant a group of atoms, in which an oxygen atom isdirectly linked to two adjacent carbon atoms or non adjacent carbonatoms comprised in a carbon containing chain or a cyclic carboncontaining system. Among epoxy functions, oxirane functions arepreferred, i.e. saturated three-membered cyclic ether groups.

Epoxysilanes compounds of formula (I) provide a highly cross-linkedmatrix. The preferred epoxysilanes have an organic link between the Siatom and the epoxy function that provides a certain level offlexibility.

The preferred Y groups are groups of formulae III and IV:

in which R² is an alkyl group, preferably a methyl group, or a hydrogenatom, ideally a hydrogen atom, a and c are integers ranging from 1 to 6,and b is 0, 1 or 2.

The preferred group having formula III is the γ-glycidoxypropyl group(R²═H, a=3, b=0) and the preferred (3,4-epoxycyclohexyl)alkyl group offormula IV is the β-(3,4-epoxycyclohexyl)ethyl group (c=1). Theγ-glycidoxyethoxypropyl group may also be employed (R²═H, a=3, b=1).

Preferred epoxysilanes of formula I are epoxyalkoxysilanes, and mostpreferred are those having one Y group and three alkoxy X groups.Particularly preferred epoxytrialkoxysilanes are those of formulae V andVI:

in which R¹ is an alkyl group having 1 to 6 carbon atoms, preferably amethyl or ethyl group, and a, b and c are such as defined above.

Examples of such epoxysilanes include but are not limited to glycidoxymethyl trimethoxysilane, glycidoxy methyl triethoxysilane, glycidoxymethyl tripropoxysilane, α-glycidoxy ethyl trimethoxysilane, α-glycidoxyethyl triethoxysilane, β-glycidoxy ethyl trimethoxysilane, β-glycidoxyethyl triethoxysilane, β-glycidoxy ethyl tripropoxysilane, α-glycidoxypropyl trimethoxysilane, α-glycidoxy propyl triethoxysilane, α-glycidoxypropyl tripropoxysilane, β-glycidoxy propyl trimethoxysilane,β-glycidoxy propyl triethoxysilane, β-glycidoxy propyl tripropoxysilane,γ-glycidoxy propyl trimethoxysilane, γ-glycidoxy propyl triethoxysilane,γ-glycidoxy propyl tripropoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 2-(3,4-epoxycyclohexyl) ethyltriethoxysilane.Other useful epoxytrialkoxysilanes are described in U.S. Pat. No.4,294,950, U.S. Pat. No. 4,211,823, U.S. Pat. No. 5,015,523, EP 0614957and WO 94/10230, which are hereby incorporated by reference. Among thosesilanes, γ-glycidoxypropyltrimethoxysilane (GLYMO) is preferred.

Preferred epoxysilanes of formula I having one Y group and two X groupsinclude, but are not limited to, epoxydialkoxysilanes such asγ-glycidoxypropyl-methyl-dimethoxysilane, γ-glycidoxypropylbis(trimethylsiloxy) methylsilane,γ-glycidoxypropyl-methyl-diethoxysilane,γ-glycidoxypropyl-methyl-diisopropenoxysilane, andγ-glycidoxyethoxypropyl-methyl-dimethoxysilane. When epoxydialkoxysilanes are used, they are preferably combined withepoxytrialkoxysilanes such as those described above, and are preferablyemployed in lower amounts than said epoxytrialkoxysilanes.

The amount of monoepoxysilane present in the intermediate coatingcomposition can be varied widely, but is preferably such that thetheoretical dry extract weight of said monoepoxysilane is higher than60% by weight, relative to the dry extract weight of the intermediatecoating composition, more preferably higher than 70%, better higher than80%, even better higher than 90% by weight. The upper limit ispreferably 99.5% by weight.

The second essential component of the intermediate coating compositionis a polyepoxy monomer, i.e. a monomer having at least 2 epoxy groups,and preferably 2 to 5 epoxy groups.

Non-limiting examples of the polyepoxy monomer comprising at least 2epoxy groups are chosen from: glycerol polyglycidyl ether; diglycerolpolyglycidyl ether; glycerol propoxylate triglycidyl ether (GPTE);trimethylolpropane triglycidyl ether; sorbitol polyglycidyl ether;poly(ethylene glycol)diglycidyl ether; poly(propylene glycol)diglycidylether; neopentyl glycol diglycidyl ether;N,N-diglycidyl-4-glycidyloxyaniline; N,N′-diglycidyltoluidine;1,6-hexane diol diglycidyl ether; diglycidyl1,2-cyclohexanedicarboxylate; diglycidyl bisphenol A; a polymer ofdiglycidyl bisphenol A; poly(bisphenol A-co-epichlorhydrin), glycidylendcapped; diglycidyl of a hydrogenated bisphenol A propylene oxideadduct; diglycidyl ester of terephthalic acid; diglycidyl1,2,3,6-tetrahydrophthalate; spiroglycoldiglycidyl ether; hydroquinonediglycidyl ether or mixtures thereof.

Other usable polyepoxy monomers are described in U.S. Pat. No. 6,984,262that is incorporated herein by reference.

Preferably, the polyepoxy monomer does not comprise any silyl group, ortheir derivatives and more preferably does not comprise any Si atom. Thepolyepoxy monomer is preferably present in an amount ranging from 0.5 to40%, preferably from 1 to 30%, better from 2 to 20% by weight relativeto the dry extract weight of the intermediate coating composition.

Another additional compound which may be used in the intermediatecoating composition comprises functionalized silane, siloxane orsilicate (alkali metal salt of a Si—OH compound), or hydrolyzatesthereof, different from the monoepoxysilanes cited above. They aregenerally substituted with one or more functional organic groups andform silica organosols and serve as binders. They may also act asadhesion promoters toward organic or mineral glass substrates.

As silicon containing binders may be cited silanes or siloxanes bearingan amine group such as amino alkoxysilanes, hydroxy silanes,alkoxysilanes, preferably methoxy or ethoxy silanes, ureidoalkylalkoxysilanes, dialkyl dialkoxysilanes (for example dimethyldiethoxysilane), vinylsilanes, allylsilanes, (meth)acrylic silanes,carboxylic silanes, polyvinylic alcohols bearing silane groups,tetraethoxysilanes, and mixtures thereof.

After having been subjected to hydrolysis, the above citedorganofunctional binders generate interpenetrated networks by formingsilanol groups, which are capable of establishing bonds with the upperlayer, namely the LbL coating and/or the underlying layer.

In one embodiment of the invention, the intermediate coating compositioncomprises at least one compound of formula:

R_(n)Si(Z)_(4-n)   (II)

or a hydrolyzate thereof, in which the R groups are identical ordifferent and represent monovalent alkyl groups, the Z groups areidentical or different and represent hydrolyzable groups or hydrogenatoms, and n is an integer equal to 0, 1 or 2, preferably 0, with theproviso that the Z groups do not all represent a hydrogen atom when n=0,and preferably do not all represent a hydrogen atom.

Compounds of formula II or their hydrolyzates may be used to improve thecross-linking of the intermediate coating obtained from the curablecomposition of the invention, thereby providing hardness andabrasion-resistance.

Silanes of formula II bear three to four Z groups directly linked to thesilicon atom, each leading to an OH group upon hydrolysis and one or twomonovalent organic R groups linked to the silicon atom. It is worthnoting that SiOH bonds may be initially present in the compounds offormula II, which are considered in this case as hydrolyzates.Hydrolyzates also encompass siloxane salts.

The Z groups may represent hydrolyzable groups independently chosen fromthe hydrolyzable groups which have been previously cited when describingthe X groups. Preferably, the Z groups are hydrolyzable groups which areidentical or different.

The most preferred R groups are C₁-C₄ alkyl groups, such as methyl,ethyl, n-propyl, i-propyl, n-butyl, i-butyl, preferably methyl groups.

Most preferred compounds of formula II are those having formula Si(Z)₄.Examples of such compounds are tetraalkoxysilanes such astetraethoxysilane Si(OC₂H₅)₄ (TEOS), tetramethoxysilane Si(OCH₃)₄(TMOS), tetra(n-propoxy)silane, tetra(i-propoxy)silane,tetra(n-butoxy)silane, tetra(sec-butoxy)silane or tetra(t-butoxy)silane,preferably TEOS.

Compounds of formula II may also be chosen from compounds of formulaRSi(Z)₃, for example methyl triethoxysilane (MTEOS).

Silanes present in the curable intermediate composition may behydrolyzed partially or totally, preferably totally. Hydrolyzates can beprepared in a known manner, e.g. such as disclosed in FR 2702486 andU.S. Pat. No. 4,211,823. Hydrolysis catalysts such as hydrochloric acidor acetic acid may be used to promote the hydrolysis reaction over thecondensation reaction.

Other additional components may be added in the composition, for examplealkoxytitanates.

The other additional compounds (except fillers described hereafter), aregenerally comprised in the intermediate coating composition in an amountranging from 1 to 20% by weight based on the total weight of theintermediate coating composition, preferably from 2 to 15%, morepreferably from 2 to 10% and even better from 2 to 5%,.

In some embodiments, the intermediate coating composition does notcomprise any additional compounds other than silanes and fillers.Preferably, the intermediate coating composition does not comprise anyadditional compounds other than silanes and fillers.

The intermediate coating composition may be cross-linked or cured owingto the presence of at least one cross-linking agent which preferably issoluble or dispersible in water. These cross-linking agents are wellknown and react with functional groups of the coating components, suchas carboxyl or hydroxyl groups. They may be chosen from polyfunctionalaziridines, methoxyalkylated melamine or urea resins, for examplemethoxyalkylated melamine/formaldehyde and urea/formaldehyde resins,epoxy resins, carbodiimides, polyisocyanates, triazines and blockedpolyisocyanates. Preferred cross-linking agents are aziridines, inparticular trifunctional aziridines.

The intermediate coating composition may also comprise a curing catalystsuch as aluminum acetylacetonate Al(AcAc)₃, a hydrolyzate thereof orcarboxylates of metals such as zinc, titanium, zirconium, tin ormagnesium. Condensation catalysts such as saturated or unsaturatedpolyfunctional acids or acid anhydrides may also be used, in particularmaleic acid, itaconic acid, trimellitic acid or trimellitic anhydride.Numerous examples of curing and/or condensation catalysts are given in“Chemistry and Technology of the Epoxy Resins”, B. Ellis (Ed.) ChapmanHall, New York, 1993 and “Epoxy Resins Chemistry and Technology” 2^(nd)edition, C. A. May (Ed.), Marcel Dekker, New York, 1988.

The intermediate coating composition optionally comprises a catalyticamount of at least one curing catalyst, so as to accelerate the curingstep. Examples of curing catalysts are photo-initiators that generatefree radicals upon exposure to ultraviolet light or heat such as organicperoxides, azo compounds, quinones, nitroso compounds, acyl halides,hydrazones, mercapto compounds, pyrylium compounds, imidazoles,chlorotriazines, benzoin, benzoin alkyl ethers, diketones, phenones, andmixtures thereof. Initiators that can induce cationic cure can also beadded to the intermediate coating composition.

In general, the catalysts and initiators described above are usedaccording to the invention in an amount ranging from 0.01 to 10%,preferably from 0.1 to 5% by weight based on the total weight of theintermediate coating composition.

In preferred embodiments, the intermediate coating composition comprisesfillers, generally nanoparticles (or nanocrystals), for increasing thehardness and/or the refractive index of the cured coating. Thenanoparticles may be organic or inorganic, preferably inorganic. Amixture of both can also be used. Preferably, inorganic nanoparticlesare used, especially metallic or metalloid oxide, nitride or fluoridenanoparticles, or mixtures thereof.

By “nanoparticles”, it is meant particles which diameter (or longestdimension) is lower than 1 μm, preferably lower than 150 nm and stillbetter lower than 100 nm. In the present invention, fillers ornanoparticles preferably have a diameter ranging from 2 to 100 nm, morepreferably from 2 to 50 nm, better from 5 to 50 nm, and optimally from10 to 20 nm.

Suitable inorganic nanoparticles are for example nanoparticles ofaluminum oxide, silicon oxide, zirconium oxide, titanium oxide, antimonyoxide, tantalum oxide, zinc oxide, tin oxide, indium oxide, ceriumoxide, silicon nitride, magnesium fluoride or their mixtures.

It is also possible to use particles of mixed oxides or compositeparticles, for example those having a core/shell structure. Usingdifferent types of nanoparticles allows making hetero-structurednanoparticles layers.

Preferably, the nanoparticles are particles of aluminum oxide, tinoxide, zirconium oxide or silicon oxide, more preferably silicon oxidenanoparticles, better SiO₂ nanoparticles. Mineral fillers are preferablyused under colloidal form, i.e. under the form of fine particlesdispersed in a dispersing medium such as water, an alcohol, a ketone, anester or mixtures thereof, preferably an alcohol.

When fillers are present, they are generally used in an amount rangingfrom 0.5 to 20% by weight of solid content based on the total weight ofthe intermediate coating composition, preferably from 1 to 15%, betterfrom 1 to 4%. The amount of solid fillers generally ranges from 1 to 50%by weight, preferably from 2% to 40%, more preferably from 5 to 35% byweight relative to the theoretical dry extract weight of theintermediate coating composition.

In some embodiments, the intermediate coating composition does notcomprise any filler such as nanoparticles.

The intermediate coating composition comprises at least one solvent,preferably a polar solvent, like water, an alcohol, or mixtures thereof,preferably a mixture of water and a water-miscible alcohol, e.g.methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol,sec-butanol, tert-butanol, n-amylic alcohol, isoamylic alcohol,sec-amylic alcohol, tert-amylic alcohol, 1-ethyl-1-propanol,2-methyl-1-butanol, 1-methoxy-2-propanol n-hexanol, cyclohexanol, ethylcellosolve (monoethoxy ethylene glycol), and ethylene glycol.

It is also possible to add an appropriate amount of another hydrophilicorganic solvent in said composition such as NMP, acetone,tetrahydrofuran, DMSO, DMAc, triethylamine or DMF.

The solvent or mixture of solvents may represent from 50 to 99% byweight, relative to the weight of the coating composition, preferablyfrom 50 to 90%, more preferably from 60 to 90%.

The coating composition may also comprise at least one nonionic or ionicsurfactant, i.e. anionic, cationic or amphoteric surfactant, to improvethe wettability of the coating solution or the optical quality of thedeposit. A particularly preferred class of surfactants comprisesfluorinated surfactants, preferably anionic fluorinated surfactants.

Fluorinated surfactants are known and described generally in“Fluorinated Surfactants” by E. Kissa, Surfactants Science Series, Vol.50 (Marcel Dekker, New York 1994). Fluorinated surfactants includeperfluoroalkanoic acids and salts thereof, in particularperfluorooctanoic acids and salts thereof, such as ammoniumperfluorooctanoic acid, fluorinated polyethers or perfluoropolyethersurfactants such as disclosed in EP 1059342, EP 712882, EP 752432, EP816397, U.S. Pat. No. 6,025,307, U.S. Pat. No. 6,103,843 and U.S. Pat.No. 6,126,849. Further fluorinated surfactants are disclosed in U.S.Pat. No. 5,229,480, U.S. Pat. No. 5,763,552, U.S. Pat. No. 5,688,884,U.S. Pat. No. 5,700,859, U.S. Pat. No. 5,804,650, U.S. Pat. No.5,895,799, WO 00/22002 and WO 00/71590. Fluorinated polyethers derivedfrom hexafluoropropyleneoxide have been described in US 2005/096244.Another class of fluorinated surfactants includes fluorocarbon modifiedpolysiloxane surfactants, e.g. polyalkyleneoxide-modifiedheptamethyltrisiloxane allyloxypolyethyleneglycol surfactant.

The surfactant or mixture of surfactants may represent from 0.001% to 5%by weight, relative to the weight of the intermediate coatingcomposition.

The composition may also contain various additives conventionally usedin polymerizable compositions, in conventional proportions. Theseadditives include stabilizers such as antioxidants, UV light absorbers,light stabilizers, anti-yellowing agents, adhesion promoters, dyes,photochromic agents, pigments, rheology modifiers, lubricants,cross-linking agents, photo-initiators fragrances, deodorants and pHregulators.

The intermediate coating composition used in the process of theinvention generally has a theoretical dry extract weight whichpreferably represents less than 50% of the total weight of thecomposition, and preferably ranging from 1 to 40%, even better from 2 to30%, which includes both required compounds and optional compounds.

By “theoretical dry extract weight of a component in a composition,” itis meant the theoretical weight of solid matter of this component insaid composition. The theoretical dry extract weight of a composition isdefined as the sum of the theoretical dry extract weights of each of itscomponents. As used herein, the theoretical dry extract weight ofcompounds of formula I or II is the calculated weight inR_(n′)YSi(O)_((3-n′)/2) or R_(n)Si(O)_((4-n)/2) units, wherein R, Y, n,and n′ are such as defined previously.

For other compounds which are not hydrolyzable, the weight taken intoaccount for the calculation of the theoretical dry extract is their ownweight.

The intermediate coating is formed at the surface of an optical articleby liquid phase deposition or lamination according to any appropriatemethod, starting from the above described liquid intermediate coatingcomposition. Application of said composition may be carried out, withoutlimitation, by spin coating, dip coating, spray coating, brush coating,roller coating. Spin coating and dip coating are preferred.

After application of the intermediate coating composition onto thesurface of the optical article, the composition may be dried or cured,if necessary, according to any appropriate method, for example dryingwith air, in an oven or by using a drier. Generally, a temperature of50-130° C. is used. The curing time may be from 10 minutes to 5 hours.The drying/curing step comprises evaporation of the solvents andsolidification of the intermediate coating composition.

Several successive depositions of intermediate coating layers accordingto the invention may be performed at the surface of the optical article.In this case, a single drying step of the whole LbL stack ofintermediate coatings is preferably performed.

Thickness of the intermediate coating in the final optical articlepreferably ranges from 50 nm to 20 microns, more preferably from 100 nmto 10 microns, even more preferably from 50 nm to 8 microns. It appearsthat the improvement of anti-fog properties is better if the thicknessof the cured intermediate coating is more than 130 nm, preferably morethan 150 nm, more preferably more than 200 nm, even better more than 250nm.

Once the intermediate coating has been applied and cured, the LbLcoating is applied and cured.

In general, the LbL coating is made on a substrate by carrying outsequential adsorption of positively charged or negatively chargedspecies by alternately dipping the substrate into coating solutionscontaining such species.

The excess or remaining solution after each adsorption step is rinsedwith a solvent.

LbL coatings have been widely described in the prior art such asUS2008/0038458, US2007/0104922, both patent applications beingincorporated herein by reference.

A typical LbL process applied to prepare an anti-fog coating on a lenssubstrate is described hereafter and is shown in FIG. 1:

-   -   I. Both sides of a lens substrate are treated with corona or        caustic solution;    -   II. The lens is first dipped in a solution comprising a first        compound having a first electric charge, for example a        polycation solution (the polycation generated from aminopropyl        functionalized silica nanoparticles in FIG. 1, ApSiO₂), followed        with an agitated rinsing step in two deionized (DI) water baths,        and then dipped in a second solution comprising a second        compound having a second electric charge which is opposite to        said first electric charge, for example a polyanion solution        (the polyanion generated from poly(acrylic acid) in FIG. 1,        PAA), followed with an agitated rinsing step in two DI water        baths. Thus a LbL coating with one bilayer of        polycation/polyanion is assembled.    -   III. Process II is repeated for (n-1) times to get a LbL coating        with n bilayers.    -   IV. The coated lens is finally cured at 100-120° C. for 1 h.    -   A polycation is a species comprising several cationic groups. A        polyanion is a species comprising several anionic groups.

An example of a possible resulting structure is represented in FIG. 2:three bilayers of polycation/polyanion on both sides of a substrate madefrom the LbL process. The resulting coating is then written as:(polycation/polyanion)₃. When a coating is made of n bilayers, theresulting coating is (polycation/polyanion)_(n).

The bilayers comprise alternated layers of polycations and polyanions.

In a first embodiment, SiO₂ nanoparticles comprising ionic groups arepositively charged and the polyelectrolyte is negatively charged.

More preferably SiO₂ nanoparticles comprising ionic groups are obtainedfrom nanoparticles functionalized by amino groups, preferably from3-aminopropylsilane modified SiO₂ nanoparticles, (polycation).

Preferably, the negatively charged polyelectrolyte is obtained from apolymer chosen from polyacrylic acid, sulfonated polystyrene, sulfonatedpolyvinylic compounds and mixtures thereof.

In a second embodiment, SiO₂ nanoparticles comprising ionic groups arenegatively charged and the polyelectrolyte is positively charged.

In this case, the polyelectrolyte is preferably obtained from a polymerchosen from poly(diallyldimethylammonium chloride), poly(allylaminehydrochloride), poly(4-vinylbenzyltrimethyl ammonium chloride) andmixtures thereof.

Non-limiting graphic formulae of polymers that can be used aspolyelectrolytes for the formation of the LbL are mentioned hereafter:

Negatively charged polyelectrolytes

Positively charged polyelectrolytes

A rinsing step, preferably in an aqueous rinsing solution is implementedafter deposition of each layer of the bi-layer or the bi-layer stack.

Preferably, said aqueous rinsing solutions have an acidic pH, preferablya pH lower than 5, more preferably lower than 4, for a LbL coatingobtained from ApSiO₂ (aminopropyl functionalized silica nanoparticles)and PAA (poly(acrylic acid)).

Preferably, each layer, in a bi-layer comprising alternately oppositelycharged species has a thickness preferably ranging from 5 to 40 nm,preferably 10 to 30 nm.

After the LbL coating has been applied, the LbL coating is submitted toa heating step at an atmospheric pressure at a temperature of 150° C. orless, preferably 140° C. or less, more preferably 130° C. or less, evenbetter 120° C. or less.

The total thickness of the LbL coating, once heated, ranges preferablyfrom 40 to 500 nm, more preferably from 50 to 200 nm, and even betterfrom 10 to 30 nm.

By atmospheric pressure, it is encompassed a pressure that can slightlyvary around 0.1 Mpa, typically from 0.08 to 0.12 MPa, preferably from0.09 to 0.101325 Mpa.

The relative humidity during heating step is generally corresponding toambient humidity, typically ranging from 40 to 60%, and preferably closeto 55%.

According to the invention, there is no treatment of the LbL coating bywater steam during the curing step of the bi-layers.

In other words, there is no hydrothermal treatment of the LbL coating,contrary to the prior art previously mentioned above wherein ahydrothermal treatment of the substrate coated with the LbL isimplemented in an autoclave.

The heating step of the LbL coating may be implemented using the sameprocess of curing than the one used for the intermediate layer of theinvention as previously described.

The invention also relates to an article bearing a LbL coating obtainedby implementing the process as previously described.

The process of the invention can be used in the ophthalmic lens industryto prepare anti-fog lenses, but also for general anti-fog purpose in thefield of photographic films, electronics or food packaging and imagingmaterials. Particular non limiting uses include windows, opticallytransparent screen for display devices and electromagnetic radiationshielding.

Its advantages are numerous and include applicability to most ofsubstrates with good adhesion, in particular plastic substrates, and theproduction of optical articles.

The preferred optical articles do preferably not absorb light in thevisible range (or little), which means herein that when coated on oneside with the inventive coating, the optical article has a luminousabsorption in the visible range due to the coatings of preferably 1% orless, more preferably less than 1%, and/or a relative light transmissionfactor in the visible spectrum, T_(v), preferably higher than 90%, morepreferably higher than 91%, and even more preferably higher than 92%.Preferably, both features are simultaneously satisfied and can bereached by carefully controlling thicknesses of the coatings. As usedherein, a “transparent” optical article is an optical article having aT_(v) higher than 90%, more preferably higher than 91%, and even morepreferably higher than 92%. The T_(v) factor is such as defined in thestandard NF EN 1836 and corresponds to the 380-780 nm wavelength range.

In an alternative embodiment, the optical article may be tinted or dyedand absorb light in the visible range.

The final optical articles prepared according to the inventionpreferably have low haze characteristics. Haze is a measurement of thetransmitted light scattered more than 2.5° from the axis of the incidentlight. The smaller the haze value, the lower the degree of cloudiness.The haze value of the present optical articles is preferably 3% or less,more preferably 1% or less, and better 0.5%.or less.

The present optical articles can be processed simply and at lowtemperature (≦120° C.), using environment friendly solvents (alcohol orwater/alcohol co-solvent). The present process is flexible and allowsincorporation of other functional coatings onto the substrate.

Now, the present invention will be described in more detail withreference to the following examples. These examples are provided onlyfor illustrating the present invention and should not be construed aslimiting the scope and spirit of the present invention.

Examples 1. Testing Methods

The following test procedures were used to evaluate the optical articlesprepared according to the present invention.

a) Dry Adhesion Test (Crosshatch Test)

Dry adhesion of the transferred coatings was measured using thecross-hatch adhesion test according to ASTM D3359-93, by cutting throughthe coatings a series of 5 lines, spaced 1 mm apart with a razor,followed by a second series of 5 lines, spaced 1 mm apart, at rightangles to the first series, forming a crosshatch pattern comprising 25squares. After blowing off the crosshatch pattern with an air stream toremove any dust formed during scribing, SCOTCH® performance flatbacktape (3M, 2525) was then applied over the crosshatch pattern, presseddown firmly, and then rapidly pulled away from coating in a directionperpendicular to the coating surface. Application and removal of freshtape was then repeated two additional times. Adhesion is rated asfollows (0 is the best adhesion, 1-4 is in the middle, and 5 is thepoorest adhesion):

TABLE 1 Adhesion score Squares removed Area % left intact 0 0 100 1<1 >96 2 1 to 4 96-84 3 >4 to 9  83-64 4 >9 to 16 63-36 5 >16 <36

b) Haze Value, Tv and Thickness

The haze value of the final optical article was measured by lighttransmission utilizing the Haze-Guard Plus haze meter from BYK-Gardner(a color difference meter) according to the method of ASTM D1003-00,which is incorporated herein in its entirety by reference. Allreferences to “haze” values in this application are by this standard.The instrument was first calibrated according to the manufacturer'sdirections. Next, the sample was placed on the transmission light beamof the pre-calibrated meter and the haze value was recorded from threedifferent specimen locations and averaged. Tv was measured using thesame device.

Thickness of the films was evaluated by ellipsometer (thickness<1 μm)equipped with M-44™, EC-270 and LPS-400 with 75W Xenon Light Source fromJ. A. Woollam Co. Inc. or with a Metricon Model 2010 Prism Couplerapparatus (thickness>1 μm) from Metricon Corporation.

c) Fog Test

Fog test used in the examples is a breath test under 23° C. with 50% RH.Immediately after breathing, the lenses are visually inspected by thenaked eye. Vision tests were at a distance of 5 meters away of targetlines (6 lines of acuity from 3/10 to 14/10). They are classified in 4categories:

-   No fog—no appearance of fog rated 1;-   Slight fog—very little fog with clear vision and low distortion of    acuity 6/10 rated 2;-   Some Fog—fog with low contrast vision and moderate distortion of    acuity 6/10 rated 3;-   Fog—very foggy without any vision of texts or with severe distortion    rated 4.

d) Hand Wiping Fog Test:

A coated substrate was hand-wiped with micro fiber cloth for 20 strokesin back and forth directions. Then after 60s, the same fog test wasconducted shown as (c).

e) Adhesion Test (Rubbing Test):

A force of 60 Newtons is applied on the front convex lens surface with aisopropyl alcohol dampened cloth covered eraser. After 10 strokes thelens was wiped off with soft cloth and then breathed upon. If the arearubbed had equal or better anti-fog performance than surrounding area,the lens is continued to be wiped an additional 10 more strokes and theprocess of checking repeated. If the area rubbed was equal to theuncoated region of the lens the lens then failed at the set of wipes itcurrently completed.

The features of the cloth and the eraser are mentioned in WO 99/49097 inthe description of the N×10 blows test.

2. Experimental Details A) General Considerations

General LbL process was applied to prepare an anti-fog coating:

-   -   I. Both sides of a lens substrate were treated with corona for        30 s using Corona Treatment System (MultiDyne™ 2) or caustic        solution (0.5 wt % NaOH) ultrasonic for 5 min;    -   II. The lens was first dipped in a polycation solution, followed        with an agitated rinsing step in two deionized (DI) water baths,        and then dipped in a polyanion solution, followed with an        agitated rinsing step in two DI water baths.    -   III. Process II was repeated for (n-1) times to get a coating        with n bilayers:

(polycation/polyinion)_(n).

-   -   IV. The coated lens was finally cured at 100-120° C. for 1 h.

B) Preparation of Coated Optical Articles

The optical articles used in the examples were round lenses (piano or−2.00 with a diameter of 68 mm) comprising an ORMA® lens substrate(obtained by polymerizing CR-39® diethylene glycol bis(allyl carbonate)monomer).

C) Preparation Process of Anti-Fog Coatings: C1-Preparation of Anti-FogCoating AF1, (ApSiO₂/PAA)₁₀

ApSiO₂: Aminopropyl functionalized silica nanoparticles, 15 nm, 3.0 w/v% from Aldrich PAA: Poly(acrylic acid), Mw=70,000 from Aldrich

The concentrations of solutions were: 0.03 wt % for ApSiO₂ and 0.01M forPAA. All solutions including the deionized water baths were titrateddown to pH 3.0 using 0.1N HCl.

Both sides of a lens substrate were treated with corona. The dippingtime in material solutions was 2 min. There were 6 sequential dips inthe first water bath and 3 sequential dips in the second water bath. Thecoated lens was cured at 120° C. for 1 h. In this experiment, thecoating bilayers were fixed as 10 bilayers with a thickness ranging from85 nm to 110 nm depending on different substrates, measured byellipsometer.

C2-Preparation of Anti-Fog Coating AF2, (PDAC/SiO₂)₁₀

PDAC: Poly(diallyidimethylammonium chloride) solution,Mw=100,000-200,000, 20 wt % in water from Aldrich

SiO₂: A2034 solution, 32-34 wt % from EKA Chemicals

The concentrations of solutions were: 0.01M for PDAC and 0.03 wt % forsilica nanoparticles. The pH of PDAC solution was 4.0; the pH of SiO₂nanoparticles was 9.0 and the pH of the deionized water baths wasdirectly used at the pH of 6.0-8.0.

Both sides of a lens substrate were treated with corona. The dippingtime in material solutions was 2 min. There were 6 sequential dips inthe first water bath and 3 sequential dips in the second water bath. Thecoated lens was cured at 120° C. for 1 h. In this experiment, thecoating bilayers were fixed as 10 bilayers with a thickness ranging from85 nm to 110 nm depending on different substrates, measured byellipsometer.

Example 1

1.1—Preparation of the Lens Substrate Coated with the IntermediateCoating (Lens Substrate S1 and S2):

1.1.1—Preparation of Solutions A and B for the Intermediate Coating.

The components of solutions A and B shown in table 1 below were preparedby adding γ-glycidoxypropyltrimethoxysilane (Glymo), KBE-402(γ-glycidoxypropylmethyldiethoxysilane (GD)), 0.1N HCl and catalystAl(AcAc)₃ under mixing. After mixing about 30 minutes, the rest ofmaterials and glycerol propoxylate triglycidyl ether (GPTE) were addedinto the mixture for another 3 hours.

TABLE 1 Intermediate coating formulation A: Weight (g) B: Weight (g)Glymo 43.25 43.25 GD (KBE-402) 128.75 128.75 0.1 N HCl 28.25 28.25Al(AcAc)3 2.00 2.00 MA-ST-HV (30-31 wt % 197.75 0 solids) Dowanol PM42.00 141.5 Methanol 40.00 138.25 EFKA 3034 0.50 0.50 GPTE 15.00 15.00Tinuvin 1130 2.50 2.50

1.1.2.—Application of the Solutions on the Lens Substrate.

A bare Orma® lens was first air blowed then corona treated. Then thelens was dipped in the solution A. The dipping withdrawal speed is 3.67mm/s. The resulting lens was then precured at 90° C. for 15 min andfinally cured at 1260° C. for 4 h, leading to lens substrates S1.

The thickness of the dry coating such obtained is 6.0 μm±0.5 μm.

The crosshatch test showed excellent adhesion of this coating to theOrma® lens substrate.

The same deposition process was reproduced using another bare Orma® lensand solution B instead of solution A, leading to lens substrate S2.

1.1.3—Application of the Anti-Fog Coating AF1

Lenses S1 and S2 obtained in 1.1.2 above were finally dipped with a LbLcoating AF1 as described above.

Bare Orma® lenses were used as comparison examples.

TABLE 2 Anti-fog Initial Fog test after Adhesion Example Lens substratecoating T, % Haze, % fog test hand wiping (Rubbing test) 1 S1 fromsolution A AF1 87.2 3.42 2 2 Passed 120 strokes 2 S2 from solution BAF1* 92.8 0.37 1 1 Scratches after 30 strokes Comparative Bare Orma AF192.3 1.07 2 3 Removed by 30 CE1 (Comparison 1) strokes *(same process asdescribed for AF1, except pH = 4.0 of all solutions in the LbL process.

Example 3

In this example, a primer layer was applied on the lens substrate,before application of the intermediate coating.

A bare (i.e. without any coating) polycarbonate (PC) lens was firstdipped in 5 wt % of aminopropyl triethoxysilane/water and dried at 75°C. for 15 min, then dipped in the solution A and cured according to thesame procedure as example 1.

The following coating procedure was same as Example 1, i.e. thedeposition of the intermediate coating from solution A, leading to alens S3 which is a lens substrate having, in this order, from thesurface of the substrate, an aminosilane primer and the intermediatecoating.

A bare PC lens was used as comparison examples.

TABLE 3 Fog test after Adhesion Lens Haze, Initial hand (Rubbing Examplesubstrate T, % % fog test wiping test) 3 S3 91.4 0.50 1 2 Passed 120strokes Comparative Bare PC 91.2 1.46 3 4 Removed example lens by 30 CE2strokes

Examples 4 to 7 and Comparative Example 3

In these examples, the thickness of the intermediate coating was varied.

Four solutions C, D, E and F shown below were prepared, by dilutingsolution A of example 1, so that solutions C, D, E and F containsrespectively 5%, 10%, 20%, and 30% of solution A.

TABLE 4 Weight (g) Solution C D E F A 5 10 20 30 Dowanol 49.875 47.2542.00 36.75 PM ™ Methanol 45.125 42.75 38.00 33.25

The convex sides of PC Airwear® lenses (these lenses have anabrasion-resistant coating based on hydrolyzed alkoxysilanes) weretreated with corona and then spin-coated at a speed of 800-1000 rpm withsolution B, C, D and E, respectively. Each sample was pre-cured at 90°C. for 15 minutes and post-cured at 126° C. for 4 h, thereby obtainingrespectively lens substrates S4, S5, S6 and S7. The features of theobtained lens substrates are mentioned in table 5. The adhesion of theintermediate coating on PC Airwear® is excellent.

TABLE 5 Intermediate Thickness of Lens Base coating intermediateAdhesion substrate substrate solution coating T, % Haze (Crosshatchtest) S4 PC C 0.128 μm 91.3 0.18 0 Airwear ® S5 PC D 0.280 μm 91.4 0.150 Airwear ® S6 PC E 0.679 μm 91.3 0.14 0 Airwear ® S7 PC F 1.095 μm 91.40.13 0 Airwear ®

Then the anti-fog coating AF1 was applied on each of these substratesfollowing the preparation process C1. The resulting lenses wereevaluated. Table 6 hereafter summarizes the results. PC Airwear®) lenswere used as comparison example.

TABLE 6 Anti-fog Fog test Lens coating Initial fog after hand AdhesionExample substrate applied T, % Haze, % test wiping (Rubbing test) 4 S4AF1 91.2 1.03 3 4 Passed 120 strokes 5 S5 AF1 90.7 1.56 2 3 Passed 120strokes 6 S6 AF1 91.5 0.59 2 2 Passed 120 strokes 7 S7 AF1 91.1 1.07 2 2Passed 120 strokes Comparative PC AF1 88.7 0.43 2 4 Removed by 90example CE3 Airwear ® strokes

Examples 8 to 10 and Comparative Example CE4

In these examples, different intermediate liquid compositions havingdifferent concentrations of epoxy monomers are used.

Four solutions for the preparation of the intermediate coating:comparison 4, G, H and I shown in table 7 below were prepared throughthe same procedure as Example 1, but with different concentrations ofGPTE.

TABLE 7 Weight (g) Comparison 4 G* H I Glymo 4.325 4.325 4.325 4.325KBE-402 12.875 12.875 12.875 12.875 0.1 N HCl 2.825 2.825 2.825 2.825Al(AcAc)₃ 0.20 0.20 0.20 0.20 MA-ST-HV 19.775 19.775 19.775 19.775Dowanol PM 237.00 236.25 235.5 234.75 Methanol 222.70 221.95 221.2220.45 EFKA 3034 0.05 0.05 0.05 0.05 GPTE 0 1.50 3.00 4.50 Tinuvin 11300.25 0.25 0.25 0.25 *The composition of dry extract weight of thecoating solution F is equivalent to that of the coating solution A.

Several PC Airwear® lenses from Essilor were coated with theintermediate coating on their convex side. They were first treated withcorona and then spin-coated at a speed of 800-1000 rpm with solutions G,H, I, and solution Comparison 4, thereby obtaining respectively coatedlens substrates S8, S9, S10, and SCE4. The sample was pre-cured at 90°C. for 15 minutes and post-cured at 126° C. for 4 h.

Then the anti-fog coating AF1 is applied on each of these substratesfollowing the preparation process C1.

Properties and features of the obtained anti-fog lens substrates aresummarized in table hereafter.

TABLE 8 Anti-fog Fog test Lens coating Initial after hand AdhesionExample substrate applied T, % Haze, % fog test wiping (Rubbing test) 8S8 AF1 90.7 1.57 2 2 Passed 120 strokes 9 S9 AF1 89.5 3.43 2 2 Passed120 strokes 10  S10 AF1 90.3 2.97 1 1 Passed 120 strokes ComparativeSCE4 AF1 91.1 1.05 3 4 Removed by 90 example strokes CE4

Examples 11 to 13 and Comparative Example CE5 to CE7 Applications toOther Hard Coated Plastic Substrates

The solution E used for the preparation of intermediate coating ofexample 5 was applied to several hard coated lenses: Orma® with a hardcoating corresponding to the coating of example 3 of EP614,957,

1.6 polythiourethane (PTU) substrate coated with an abrasion resistantcoating comprising a hydrolyzate of an epoxyalkoxysilane and a highindex colloid and 1.67 polythiourethane (PTU) substrate coated with anabrasion resistant coating comprising a hydrolyzate of anepoxyalkoxysilane and a high index colloid, designated respectively assubstrate S11, S12 and S13.

In each case, a lens without the intermediate layer was used as thecomparison example.

All coating substrates were dipped with AF1 according to the procedureshown before in C1.

TABLE 9 Anti- Lens fog Initial Fog test after Adhesion Example substratecoating T, % Haze, % fog test hand wiping (Rubbing test) 11 S11 AF1 89.62.85 2 2 Passed 120 strokes CE5 Hard coated AF1 90.1 2.60 4 4 Removed by60 Orma ® strokes 12 S12 AF1 88.9 2.88 1 2 Passed 120 strokes CE6 Hardcoated AF1 89.7 2.72 4 4 Removed by 30 PTU 1.6 strokes 13 S13 AF1 88.82.40 2 2 Passed 120 strokes CE7 Hard coated AF1 91.8 1.17 4 4 Removed by30 PTU 1.67 strokes

Examples 14 to 17 and Comparative Experiment CE8

In these examples, the anti-fog coating AF2 is applied.

The convex sides of PC Airwear® lenses were treated with corona and thenspin-coated at the speed of 800-1000 rpm with an intermediate coatingsolution C, D E or F, respectively (as used in previous examples 4 to 7)according to the same process described in Example 4, leadingrespectively to lens substrates S14, S15, S16, S17. Then anti-fogcoating AF2 is applied as described in C2 above. PC Airwear® lens wasused as a comparison example.

TABLE 10 Lens Anti-fog coating Initial Fog test after Adhesion afterhand Examples substrate applied fog test hand wiping wiping 14 S14 AF2 34 Coating remained with some visual scratches 15 S15 AF2 2 3 Coatingremained with partial visual scratches 16 S16 AF2 2 3 Coating remainedwith small visual scratches 17 S17 AF2 2 3 Coating remained withoutvisual scratches CE8 PC AF2 3 4 Completely removed Airwear ®

Examples 18 to 20 and Comparative Example 9

Three solutions J, K, and L shown below in table 11 were preparedthrough the same procedure as Example 1, but with different epoxymonomers.

TABLE 11 Weight (g) J K L Glymo 25.95 25.95 25.95 KBE-402 77.25 77.2577.25 0.1 N HCl 16.95 16.95 16.95 Al(AcAc)₃ 1.2 1.2 1.2 MA-ST-HV 118.65 118.65  118.65  Dowanol PM 20.7  20.7  20.7  Methanol 19.5  19.5  19.5 EFKA 3034 0.3 0.3 0.3 Epoxy 18*   18**   18*** Tinuvin 1130 1.5 1.5 1.5*EGDE: Ethylene glycol diglycidyl ether **TMPTGE: Trimethylol propanetriglycidyl ether ***GDE: Glycerol diglycidyl ether

Both sides of Orma® lenses were treated with corona and then dip-coatedin the solution J K, or L, leading respectively to corresponding lenssubstrates S18, S19 and S20. The dipping speed was 110 mm for 35seconds. The lens substrates were pre-cured at 90° C. for 15 minutes andpost-cured at 126° C. for 4 h. The thickness of dry intermediatecoatings made from J, K, or L corresponding respectively to lenssubstrates S18, S19 and S20 are 6.7±0.5 μm. After the coatings cooleddown, both sides of lenses were treated with corona and deposited withAF2 as described in point C2 before. Orma® lens coated with AF2 was usedas a comparison example

TABLE 12 Anti-fog Fog test Lens coating Initial after hand Adhesionafter Example substrate applied T, % Haze, % fog test wiping hand wiping18 S18 AF2 94.2 0.28 2 2 Coating remained with no visual scratches 19S19 AF2 94.2 0.28 2 3 Coating remained with no visual scratches 20 S20AF2 95.3 0.31 2 3 Coating remained with no visual scratches CE9 Orma ®AF2 94.6 0.31 2 4 Coating remained with many visual scratches

From the previous examples, it appears that the intermediate coatingfulfills two different functions:

1)The intermediate coating of the invention increases the anti-fogproperties of the anti-fog LbL coating deposited thereon (in comparisonto lens substrates treated with the same anti-fog LbL coating applieddirectly on the substrate that does not comprise the intermediatecoating).

This is an immediate effect, i.e. it can be seen immediately afterpreparation of the anti-fog lens substrate.

2)The intermediate coating of the invention improves mechanicaldurability of the anti-fog coating.

It also appears that ApSiO₂/PAA coatings have stronger adhesion thanPDAC/SiO₂ coatings on the tested lens substrates.

Thus the rubbing test (N×10 blows) which is more severe than hand wipingwas applied for ApSiO2/PAA coatings and the hand wiping test forPDAC/SiO₂ coatings, in order to distinguish the difference of coatingadhesion.

Overall, adhesion and antifog improvements of the LbL coatings was alsoobserved using intermediate layer formulated without nanoparticles.

1.-19. (canceled)
 20. A process for preparing an article having anti-fogproperties, comprising: a) providing a substrate having at least onemain surface coated with an intermediate coating obtained by applyingand at least partially curing an intermediate coating compositioncomprising at least one monoepoxysilane and/or an hydrolyzate thereofand at least one polyepoxy monomer comprising at least two epoxy groups;b) forming onto said intermediate coating at least one bi-layer obtainedby: b1—forming a first layer by applying a first layer composition onsaid intermediate coating, said first layer composition comprising atleast one compound A having a first electric charge, b2—forming a secondlayer by applying a second layer composition directly on said firstlayer, said second layer composition comprising at least one compound Bhaving a second electric charge which is opposite to said first electriccharge, compounds A and B being independently chosen frompolyelectrolytes, SiO₂ nanoparticles comprising ionic groups and TiO₂nanoparticles comprising ionic groups, with the proviso that at leastone of said first and said second layer comprises SiO₂ nanoparticlescomprising ionic groups and/or TiO₂ nanoparticles comprising ionicgroups; and c) curing said at least one bi-layer by heating at atemperature of 150° C. or less, at atmospheric pressure and in theabsence of added water steam.
 21. The process of claim 20, wherein atleast one of said first and said second layer comprises SiO₂nanoparticles comprising ionic groups.
 22. The process of claim 20,wherein the at least one bi-layer is cured by heating at a temperatureof 120° C. or less, at atmospheric pressure and in the absence of addedwater steam.
 23. The process of claim 20, wherein one of the layers ofsaid at least one bi-layer comprises SiO₂ nanoparticles comprising ionicgroups and the other layer of said at least one bi-layer comprises atleast one oppositely charged polyelectrolyte.
 24. The process of claim23, wherein the SiO₂ nanoparticles comprising ionic groups arepositively charged.
 25. The process of claim 24, wherein the SiO₂nanoparticles comprising ionic groups are obtained from nanoparticlesfunctionalized by amino groups.
 26. The process of claim 25, wherein theSiO₂ nanoparticles comprising ionic groups are obtained from3-aminopropylsilane modified SiO₂ nanoparticles.
 27. The process ofclaim 24, wherein the polyelectrolyte is negatively charged.
 28. Theprocess of claim 27, wherein the polyelectrolyte is obtained from apolymer further defined as a polyacrylic acid, sulfonated polystyrene,sulfonated polyvinylic compound or a mixture thereof.
 29. The process ofclaim 23, wherein the SiO₂ nanoparticles comprising ionic groups arenegatively charged.
 30. The process of claim 29, wherein thepolyelectrolyte is positively charged.
 31. The process of claim 30,wherein the polyelectrolyte is a polymer further defined as apoly(diallyl dimethylammonium chloride), poly(allylamine hydrochloride),poly(4-vinylbenzyltrimethyl ammonium chloride) or a mixture thereof. 32.The process of claim 20, wherein the monoepoxysilane is a compound offormula:R_(n′)YSi(X)_(3-n′)  (I) or a hydrolyzate thereof, in which the R groupsare identical or different and represent monovalent organic groupslinked to the silicon atom through a carbon atom, Y is a monovalentorganic group linked to the silicon atom through a carbon atom andcontaining one epoxy function, the X groups are identical or differentand represent hydrolyzable groups or hydrogen atoms, and n′ is 0 or 1.33. The process of claim 20, wherein the polyepoxy monomer is furtherdefined as a glycerol propoxylate triglycidyl ether, trimethylolpropanetriglycidyl ether, or a mixture thereof.
 34. The process of claim 20,wherein the polyepoxy monomer has two to four epoxy groups.
 35. Theprocess of claim 34, wherein the polyepoxy monomer is present in theintermediate coating composition in an amount ranging from 0.5 to 40% byweight relative to the weight of the dry extract of said intermediatecoating composition.
 36. The process of claim 20, wherein saidintermediate coating composition further comprises at least oneinorganic filler.
 37. The process of claim 20, wherein the thickness ofsaid intermediate coating ranges from 50 nm to 20 microns.
 38. Theprocess of claim 20, wherein each layer of said at least one bi-layer isrinsed with an aqueous rinsing solution after having been deposited. 39.The process of claim 20, wherein the intermediate coating is coated witha plurality of said bi-layers stacked onto each other, with the provisothat the second electric charge of the at least one compound B comprisedin the second layer of each bi-layer is opposite to the first electriccharge of the at least one compound A comprised in the first layer ofthe subsequent bi-layer.
 40. An optical article comprising a substratecoated with an anti-fog coating, obtainable by the process of claim 20.